CN110642257B - Method for preparing silicon dioxide aerogel by using silicon micropowder - Google Patents
Method for preparing silicon dioxide aerogel by using silicon micropowder Download PDFInfo
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- CN110642257B CN110642257B CN201910997559.9A CN201910997559A CN110642257B CN 110642257 B CN110642257 B CN 110642257B CN 201910997559 A CN201910997559 A CN 201910997559A CN 110642257 B CN110642257 B CN 110642257B
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/113—Silicon oxides; Hydrates thereof
- C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
- C01B33/14—Colloidal silica, e.g. dispersions, gels, sols
- C01B33/157—After-treatment of gels
- C01B33/158—Purification; Drying; Dehydrating
- C01B33/1585—Dehydration into aerogels
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/12—Surface area
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Abstract
The invention discloses a method for preparing silicon dioxide aerogel by utilizing silicon micropowder, which relates to the technical field of inorganic oxide processing, and takes the silicon micropowder as an inorganic silicon source, thereby reducing the cost and improving the production safety of the silicon dioxide aerogel; when the sol is prepared, the silicic acid product exists in a liquid state, the calcium sulfate serving as a byproduct exists in a precipitate form, and the calcium sulfate can be removed by filtering out the precipitate; the silica aerogel can be prepared by subsequent aging, dewatering and drying operations of the silica sol, and the average particle size of the prepared silica aerogel is 15-30nm, and the specific surface area is 500m2More than g.
Description
The technical field is as follows:
the invention relates to the technical field of inorganic oxide processing, in particular to a method for preparing silicon dioxide aerogel by utilizing silicon micropowder.
Background art:
the silica aerogel is a lightweight material with nano-porosity, and has unique properties in the aspects of mechanics, acoustics, heat, optics and the like. The porosity of the silicon dioxide aerogel is as high as 80-99.8%, the pore size is about 1-100nm, and the specific surface area is as high as 200-2G, density variation can reach 3-500kg/m3The composite material has the advantages of low heat conductivity coefficient, good heat insulation performance, strong adsorption performance and the like.
The commonly used preparation method of the silicon dioxide aerogel comprises two processes of sol-gel and supercritical drying, wherein substances such as methyl orthosilicate or ethyl orthosilicate and the like are mostly adopted as an organic silicon source, but the price of the organic silicon source is high, so that the final aerogel product is high in cost; the organic silicon source has certain toxicity, and causes pollution to human bodies and the environment in the production process; in addition, the supercritical drying technology needs high-temperature and high-pressure equipment, has high energy consumption and high operation cost, and is not easy to realize large-scale production.
The invention content is as follows:
the technical problem to be solved by the invention is to provide a method for preparing silicon dioxide aerogel by utilizing silicon micropowder, which reduces the cost, improves the production safety, and simultaneously ensures that the average particle size of the prepared silicon dioxide aerogel is 15-30nm and the specific surface area is 500m2More than g.
The technical problem to be solved by the invention is realized by adopting the following technical scheme:
a method for preparing silicon dioxide aerogel by utilizing silicon micropowder comprises the following steps:
(1) and (3) calcining: mixing the silicon micropowder with calcium oxide, and calcining at high temperature;
(2) preparation of silica sol: adding dilute sulfuric acid into the calcined product for reaction, and filtering out precipitates after the reaction is finished to obtain silicon dioxide sol;
(3) preparation of silica gel: placing and aging the silica sol to obtain silica gel;
(4) dewatering: adding absolute ethyl alcohol into the silica gel to remove residual water in gel gaps;
(5) and (3) drying: and (3) carrying out ultrasonic freezing treatment on the silicon dioxide gel subjected to the water removal by utilizing an ultrasonic-assisted freezing technology, and finally drying at low temperature to obtain the silicon dioxide aerogel.
The molar ratio of the silicon dioxide to the calcium oxide in the silicon micro powder is 1: 0.8-1.2.
The calcination temperature was 850 ℃.
The volume concentration of the dilute sulfuric acid is 3-10%.
The aging time is 5-24 h.
The conditions of the ultrasonic wave auxiliary freezing technology are that the ultrasonic frequency is 40KHz, the ultrasonic power is 1000W, and the freezing temperature is-15 ℃.
The temperature of the low-temperature drying is 80 ℃.
The cavitation effect and the mechanical effect generated by the ultrasonic wave in the medium transmission process are utilized to promote the formation of the aerogel and control the formation process of the aerogel, and meanwhile, the freezing condition can promote the aerogel structure to reach a stable state, so that the silicon dioxide aerogel with narrow particle size distribution range and high porosity is prepared.
In order to prevent the particle size distribution range of the prepared silica aerogel from being uncontrollable due to agglomeration of silica particles in the aging process, the anti-agglomeration agent is added into the silica sol and then placed for aging, namely, the step (3) in the technical scheme can be replaced by adding the anti-agglomeration agent into the silica sol and then placing for aging to obtain the silica gel, and the rest steps and control parameters are the same as those in the technical scheme.
The anti-agglomeration agent is a sodium gluconate aqueous solution with the mass concentration of 30%.
The anti-agglomeration agent is replaced and removed along with water because the anti-agglomeration agent is dissolved in the water in the subsequent water removal operation. The prior art in the field does not report the technical proposal of using an anti-agglomeration agent in the aging process of the silica gel to control the particle size of the prepared silica aerogel.
The invention has the beneficial effects that: according to the invention, the silicon micropowder is used as an inorganic silicon source, so that the production safety of the silicon dioxide aerogel is improved while the cost is reduced; when the sol is prepared, the silicic acid product exists in a liquid state, the calcium sulfate serving as a byproduct exists in a precipitate form, and the calcium sulfate can be removed by filtering out the precipitate; the silica aerogel can be prepared by subsequent operations of aging, dewatering and drying, and the average particle size of the prepared silica aerogel is 15-30nm, and the specific surface area is 500m2More than g.
The specific implementation mode is as follows:
in order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further described with the specific embodiments.
Example 1
(1) And (3) calcining: mixing 1 kg of silicon micropowder with calcium oxide, wherein the molar ratio of silicon dioxide to calcium oxide in the silicon micropowder is 1: 1, and calcining at 850 ℃ for 1 h;
(2) preparation of silica sol: adding 5% dilute sulfuric acid into the calcined product to react for 1 hour, wherein the use amount of the dilute sulfuric acid is to adjust the pH value of the reaction solution to 6-7, and filtering out precipitates after the reaction is finished to obtain silicon dioxide sol;
(3) preparation of silica gel: placing the silica sol at 25 ℃ and aging for 10 h to obtain silica gel;
(4) dewatering: adding absolute ethyl alcohol into the silica gel, replacing for three times, wherein 500 mL of absolute ethyl alcohol is used for each replacement, and removing residual water in gel gaps;
(5) and (3) drying: and (3) carrying out ultrasonic wave freezing treatment on the dehydrated silica gel for 0.5 h by utilizing an ultrasonic wave auxiliary freezing technology, wherein the ultrasonic wave frequency is 40KHz, the ultrasonic power is 1000W, the freezing temperature is-15 ℃, and finally, drying at a low temperature of 80 ℃ for 5 h to obtain the silica aerogel.
Example 2
The ultrasonic freezing treatment in example 1 was prolonged to 1 hour, and the procedure was as in example 1.
Example 3
Example 1 was repeated except that "30% aqueous sodium gluconate solution was added to the silica sol and the mixture was aged at 25 ℃ for 10 hours to obtain silica gel" in step (3) of example 1.
Comparative example
The procedure of example 1 was followed except that "the silica gel after water removal was dried at a low temperature of 80 ℃ for 5 hours to obtain a silica aerogel" in step (5) of example 1.
Silica aerogels were prepared using the above examples and comparative examples, respectively, and their average particle diameters and specific surface areas were measured using a JCM-7000 scanning electron microscope, with the results shown in table 1.
TABLE 1 average particle diameter and specific surface area of silica aerogel
| Item | Example 1 | Example 2 | Example 3 | Comparative example |
| Average particle diameter of nm | 15-30 | 15-30 | 15-25 | 15-80 |
| Specific surface area m2/g | 528 | 546 | 617 | 345 |
As can be seen from table 1, the present invention can achieve the technical effects of controlling the average particle size of the prepared silica aerogel and significantly increasing the specific surface area through the ultrasonic freezing treatment and the application of the anti-agglomeration agent.
The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (5)
1. A method for preparing silicon dioxide aerogel by using silicon micropowder is characterized by comprising the following steps:
(1) and (3) calcining: mixing the silicon micropowder with calcium oxide, and calcining at high temperature;
(2) preparation of silica sol: adding dilute sulfuric acid into the calcined product for reaction, and filtering out precipitates after the reaction is finished to obtain silicon dioxide sol;
(3) preparation of silica gel: placing and aging the silica sol to obtain silica gel;
(4) dewatering: adding absolute ethyl alcohol into the silica gel to remove residual water in gel gaps;
(5) and (3) drying: carrying out ultrasonic freezing treatment on the silicon dioxide gel after water removal by using an ultrasonic-assisted freezing technology, and finally drying at low temperature to obtain silicon dioxide aerogel;
the conditions of the ultrasonic-assisted freezing technology are that the ultrasonic frequency is 40KHz, the ultrasonic power is 1000W, and the freezing temperature is-15 ℃;
the calcination temperature was 850 ℃.
2. The method for preparing silica aerogel using silica micropowder according to claim 1, wherein: the molar ratio of the silicon dioxide to the calcium oxide in the silicon micro powder is 1: 0.8-1.2.
3. The method for preparing silica aerogel using silica micropowder according to claim 1, wherein: the volume concentration of the dilute sulfuric acid is 3-10%.
4. The method for preparing silica aerogel using silica micropowder according to claim 1, wherein: the aging time is 5-24 h.
5. The method for preparing silica aerogel using silica micropowder according to claim 1, wherein: the temperature of the low-temperature drying is 80 ℃.
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Citations (5)
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|---|---|---|---|---|
| CN102795631A (en) * | 2012-06-19 | 2012-11-28 | 刘相红 | Method for preparing silicon dioxide aerogel |
| CN107010632A (en) * | 2017-05-26 | 2017-08-04 | 南京林业大学 | A kind of preparation method of biomass-based nanometer titanium dioxide silica aerogel |
| CN107473251A (en) * | 2017-08-30 | 2017-12-15 | 浙江德赛堡建筑材料科技有限公司 | A kind of preparation method of nanoscale calcium hydroxide |
| CN109678189A (en) * | 2019-01-09 | 2019-04-26 | 无锡日月水处理有限公司 | A kind of calcium hydroxide high efficiency preparation method |
| MX2017014304A (en) * | 2017-11-08 | 2019-05-09 | Univ Mexico Nac Autonoma | Use of cryogels with ultrasound-assisted diffusion to limit the growth of ice crystals in the food freezing process. |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102795631A (en) * | 2012-06-19 | 2012-11-28 | 刘相红 | Method for preparing silicon dioxide aerogel |
| CN107010632A (en) * | 2017-05-26 | 2017-08-04 | 南京林业大学 | A kind of preparation method of biomass-based nanometer titanium dioxide silica aerogel |
| CN107473251A (en) * | 2017-08-30 | 2017-12-15 | 浙江德赛堡建筑材料科技有限公司 | A kind of preparation method of nanoscale calcium hydroxide |
| MX2017014304A (en) * | 2017-11-08 | 2019-05-09 | Univ Mexico Nac Autonoma | Use of cryogels with ultrasound-assisted diffusion to limit the growth of ice crystals in the food freezing process. |
| CN109678189A (en) * | 2019-01-09 | 2019-04-26 | 无锡日月水处理有限公司 | A kind of calcium hydroxide high efficiency preparation method |
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| Title |
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| Effect of ultrasound irradiation on ice crystal size distribution in frozen agar gel samples;Hossein Kiani et al.;《Innovative Food Science and Emerging Technologies》;20131231;第18卷;第126-131页 * |
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